The present invention relates to a coupling site for use in medical applications and more particularly, to a coupling site which includes a valve element and support structure for cooperation with a standard male luer lock having a male luer taper and a threaded locking collar.
In recent years there has been increased concern with the spread of infectious diseases which may result from puncture wounds made by medical needles. There is also concern with the inconvenience of handling devices having needles which may inflict painful puncture wounds and which may be easily broken. However, needles have continued to be used in association with injection sites or other coupling sites in medical applications to transfer fluids to and from syringes or fluid conveying cannula. The continued use of needles for such coupling sites may be attributed to the convenience with which a needle may be inserted through a soft diaphragm wherein a fluid-tight seal is formed around the needle and, subsequently the needle may be withdrawn from the diaphragm resulting in the diaphragm resiliently filling in and closing the aperture formed by the needle. Thus, needle type injection sites have the advantages of providing quick access for a fluid cannula as well as providing an access site which ensures a fluid-tight seal due to the small size of the aperture formed in the diaphragm by the needle.
In spite of the advantages associated with needle type injection sites, there is a recognized need for replacing such an injection site with one which eliminates the needle in order to avoid the disadvantages associated therewith including the possibility of medical personnel receiving a puncture wound during the use thereof and the progressive deterioration of the diaphragm resulting from repetitive puncturing of the diaphragm.
One proposed solution for eliminating needles at coupling sites includes providing a valve member having a slit for receiving a blunt cannula therethrough wherein the slit is biased to a closed position such that a fluid-tight seal is formed at the valve member when the cannula is removed.
U.S. Pat. No. 4,765,588 to Atkinson discloses a valve for receiving the blunt end of a syringe and includes a slit diaphragm member mounted within a tubular body wherein the diaphragm is stretched in the area of the slit and moves in close to the tubular body as a luer taper portion of the syringe is inserted. In addition, the exterior wall of the body portion is dimensioned to be received within a threaded locking collar of the syringe surrounding the luer taper whereby an additional fluid-tight seal is formed with the valve.
It has been recognized that it is not only desirable to provide a valve adapted to receive a blunt cannula such as the luer taper of a syringe, as is disclosed by the above Atkinson patent, it is also desirable to provide a connection or coupling which positively locks the blunt cannula to the coupling site and thereby prevents inadvertent removal of the cannula during use. A concept for providing a mechanical lock between a blunt cannula and an injection site is disclosed in PCT Publication No. WO 90/11103 which discloses an injection site having a housing mounting a preslit septum and means for mechanically coupling a specially adapted cannula to the housing. One such special cannula contemplates providing a female luer connection for threadably engaging within the threaded locking collar of a male luer lock fitting on a syringe and further includes a specially configured blunt cannula having a tapered end for passing through the preslit septum of the valve. In addition, the housing holding the septum may be provided with threads for engaging coupling threads located interiorly of a shield surrounding the cannula.
It should be noted that in the above-described site, the outer diameter of the housing is formed larger than the inner diameter of the threaded collar on the syringe in order to provide sufficient space for the septum which expands outwardly into an annular space during insertion of a cannula.
There is a need for a medical coupling site that is usable with blunt cannula such as are provided by standard male luer lock fittings having a male luer taper surrounded by a threaded locking collar and in which the site is provided with a valve element and means for directly engaging the threads on the locking collar to form a mechanical connection. It should be noted that such a site is highly desirable in that standard dimensions for both male and female luer taper fittings have been recognized by both the American National Standards Institute, Inc. (ANSI) and by the International Organization for Standardization (ISO). Thus, the fittings formed on the ends of syringes, as well as fittings for the majority fluid connections used in medical applications throughout the world, conform to the ANSI and ISO standards and a coupling site incorporating a valve for use with such standard fittings would provide the advantage of allowing a positive mechanical connection to be formed at the coupling site as well as eliminate the need for the use of needles or special cannula to penetrate the valve element, and thus would overcome disadvantages associated with prior art coupling sites.
Elimination of the need for a special cannula for use at the coupling site would also provide a cost advantage in that only the coupling site would need to be purchased and existing fittings could be used in conjunction with this site.
One problem associated with providing a coupling site for use with a standard male luer lock results from the limited space provided between the outer surface of the male luer taper and the inner surface of the threaded locking collar which makes it difficult to provide both a rigid locking surface on the outside of the fitting for engaging the locking collar and a flexible valve element of sufficient size and resilience to releasably accommodate the male luer taper.
Thus, the Atkinson patent described above describes a valve element which may be used with a luer fitting, but in which the outer surface of the elastomeric valve element is received in contact with the locking collar without the inclusion of any rigid member for engaging the threads within the collar. The PCT publication described above discloses an alternative approach to the same problem in that the adapter provided for attachment to a standard luer lock is provided with a locking collar which is larger than the locking collar provided on the male luer lock, thus permitting the coupling site to be constructed with an enlarged diameter to accommodate a sufficiently large septum for receiving a cannula having the desired diameter for providing sufficient flow through the site.
There are certain physical design limitations to providing a valve element which will both receive a luer taper as well as reliably reseal after the luer taper is removed. Several prior art valves for receiving a luer taper provide a thick disk or septum, such as is disclosed in the above-noted PCT publication, wherein the disk or septum is formed with a sufficient amount of resilient material around the slit to close the slit when a cannula is not present. Space must be provided in order to accommodate the distortion of material around the slit as the cannula is inserted and this space must either be provided within the fluid passage area for receiving the cannula or within the housing supporting the disk or septum, such as may be provided by an annular space directly adjacent to the outer periphery of the disk or septum.
Alternatively, the slit may be formed in a relatively thin diaphragm, such as is disclosed in the Atkinson patent, wherein sufficient space for receiving the distorted portions of the diaphragm around the slit is provided within a space defined by a tubular body portion for receiving the luer taper.
Thus, it is apparent that in any coupling site sufficient space must be provided around the circumference of any valve member in order to accommodate distortion of the resilient material forming the valve member such that little space is available for additionally accommodating a rigid member adapted to engage the threaded locking collars surrounding the male luer taper. Further, if the material surrounding the slit portion of the valve element is reduced, the forces provided by the material to resiliently bias the slit to a closed position are also reduced and thus may result in an undesirable structure which will not positively seal the slit closed upon removal of a cannula or luer taper.
It should further be noted that it is preferable to provide a coupling site which is adapted to receive cannula having a diameter at least as large as a standard male luer taper in order to avoid introducing any restriction to flow at the site with resulting reductions in the flow rate.
A further problem associated with prior art coupling sites relates to the ability of an operator to effectively clean the exterior of the site prior to insertion of a cannula. Ideally, the exposed surface at the end of the site for receiving the cannula is formed with a perfectly smooth contour. However, this has not proven to be practical in prior art sites in that the sites have typically incorporated a resilient septum which is compressed between rigid housing portions at upper and lower surfaces of the septum to frictionally grip the peripheral edges of the septum. While this construction is effective for holding the septum in place relative to the housing, the exposed surfaces of the housing and septum, at the point where the housing meets the septum, generally defines a crevice as a result of the housing surface being oriented at a different angle than the surface of the septum. Thus, it has been difficult in prior art coupling sites to ensure that the exposed surfaces are thoroughly wiped clean prior to insertion of a cannula while also providing a structure for effectively preventing the resilient portion of the site from moving relative to the surrounding rigid housing.
Accordingly, there is a need for a medical fluid path coupling site which may be coupled directly to a standard male luer lock including means for forming a mechanical connection with a threaded locking collar portion of the luer lock. In addition, there is a need for such a site including a valve in which a slit for receiving a male luer taper portion of the male luer lock is positively biased to a closed position to prevent leakage through the valve when the male luer taper is removed.
Further, there is a need for a medical coupling site wherein the resilient and rigid portions of the site are positively engaged with each other to prevent relative movement, and wherein exposed junctions between the resilient and rigid members define an easily wiped surface.